<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>NaN</title>
</head>
<body>
    <script>
        // console.log(NaN, typeof NaN); //'numble'
        // console.log(0 / 0, 6 / 0,-6/0);// NaN Infinity -Infinity
        // console.log(Math.sqrt(-1));
        // console.log("abc"-10);
        // console.log(undefined + 5);
        // console.log(parseInt("hello"));
        const a = 0 / 0;
        const b = parseInt("hello");
        if(Number.isNaN(parseInt("hello"))){
            console.log('不是一个数字，不能继续计算了');
        }
// • javaScript 中 正数除以 0 返回 Infinity 
// • 负数除以 0 返回 -Infinity 
// • 0/0 才会返回 NaN
        
    </script>
</body>
</html>